Open Source Computer Vision Library https://opencv.org/
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.. _widget_pose:
Pose of a widget
****************
Goal
====
In this tutorial you will learn how to
.. container:: enumeratevisibleitemswithsquare
* Add widgets to the visualization window
* Use Affine3 to set pose of a widget
* Rotating and translating a widget along an axis
Code
====
You can download the code from :download:`here <../../../../samples/cpp/tutorial_code/viz/widget_pose.cpp>`.
.. code-block:: cpp
#include <opencv2/viz/vizcore.hpp>
#include <opencv2/calib3d/calib3d.hpp>
#include <iostream>
using namespace cv;
using namespace std;
/**
* @function main
*/
int main()
{
/// Create a window
viz::Viz3d myWindow("Coordinate Frame");
/// Add coordinate axes
myWindow.showWidget("Coordinate Widget", viz::WCoordinateSystem());
/// Add line to represent (1,1,1) axis
viz::WLine axis(Point3f(-1.0f,-1.0f,-1.0f), Point3f(1.0f,1.0f,1.0f));
axis.setRenderingProperty(viz::LINE_WIDTH, 4.0);
myWindow.showWidget("Line Widget", axis);
/// Construct a cube widget
viz::WCube cube_widget(Point3f(0.5,0.5,0.0), Point3f(0.0,0.0,-0.5), true, viz::Color::blue());
cube_widget.setRenderingProperty(viz::LINE_WIDTH, 4.0);
/// Display widget (update if already displayed)
myWindow.showWidget("Cube Widget", cube_widget);
/// Rodrigues vector
Mat rot_vec = Mat::zeros(1,3,CV_32F);
float translation_phase = 0.0, translation = 0.0;
while(!myWindow.wasStopped())
{
/* Rotation using rodrigues */
/// Rotate around (1,1,1)
rot_vec.at<float>(0,0) += CV_PI * 0.01f;
rot_vec.at<float>(0,1) += CV_PI * 0.01f;
rot_vec.at<float>(0,2) += CV_PI * 0.01f;
/// Shift on (1,1,1)
translation_phase += CV_PI * 0.01f;
translation = sin(translation_phase);
Mat rot_mat;
Rodrigues(rot_vec, rot_mat);
/// Construct pose
Affine3f pose(rot_mat, Vec3f(translation, translation, translation));
myWindow.setWidgetPose("Cube Widget", pose);
myWindow.spinOnce(1, true);
}
return 0;
}
Explanation
===========
Here is the general structure of the program:
* Create a visualization window.
.. code-block:: cpp
/// Create a window
viz::Viz3d myWindow("Coordinate Frame");
* Show coordinate axes in the window using CoordinateSystemWidget.
.. code-block:: cpp
/// Add coordinate axes
myWindow.showWidget("Coordinate Widget", viz::WCoordinateSystem());
* Display a line representing the axis (1,1,1).
.. code-block:: cpp
/// Add line to represent (1,1,1) axis
viz::WLine axis(Point3f(-1.0f,-1.0f,-1.0f), Point3f(1.0f,1.0f,1.0f));
axis.setRenderingProperty(viz::LINE_WIDTH, 4.0);
myWindow.showWidget("Line Widget", axis);
* Construct a cube.
.. code-block:: cpp
/// Construct a cube widget
viz::WCube cube_widget(Point3f(0.5,0.5,0.0), Point3f(0.0,0.0,-0.5), true, viz::Color::blue());
cube_widget.setRenderingProperty(viz::LINE_WIDTH, 4.0);
myWindow.showWidget("Cube Widget", cube_widget);
* Create rotation matrix from rodrigues vector
.. code-block:: cpp
/// Rotate around (1,1,1)
rot_vec.at<float>(0,0) += CV_PI * 0.01f;
rot_vec.at<float>(0,1) += CV_PI * 0.01f;
rot_vec.at<float>(0,2) += CV_PI * 0.01f;
...
Mat rot_mat;
Rodrigues(rot_vec, rot_mat);
* Use Affine3f to set pose of the cube.
.. code-block:: cpp
/// Construct pose
Affine3f pose(rot_mat, Vec3f(translation, translation, translation));
myWindow.setWidgetPose("Cube Widget", pose);
* Animate the rotation using wasStopped and spinOnce
.. code-block:: cpp
while(!myWindow.wasStopped())
{
...
myWindow.spinOnce(1, true);
}
Results
=======
Here is the result of the program.
.. raw:: html
<div align="center">
<iframe width="420" height="315" src="https://www.youtube.com/embed/22HKMN657U0" frameborder="0" allowfullscreen></iframe>
</div>